Synced practice exercise metadata to problem specifications. (#3922)

Author: BethanyG

exercises/practice/simple-cipher/.meta/config.json

@@ -30,7 +30,7 @@
       ".meta/example.py"
     ]
   },
-  "blurb": "Implement a simple shift cipher like Caesar and a more secure substitution cipher.",
+  "blurb": "Implement the Vigenère cipher, a simple substitution cipher.",
   "source": "Substitution Cipher at Wikipedia",
   "source_url": "https://en.wikipedia.org/wiki/Substitution_cipher"
 }